In a saucepan, heat coconut milk. Add sugar, salt, cornstarch and water. Cook over medium heat and stir constantly until mixture thickens. Stir in flavoring. Take off heat and cool until warm. Poke holes in cake with a bamboo skewer. Pour about 1/2 cup of coconut milk mixture onto the cake and spread to cover. Let cool. 'Frost' the cake with remaining mixture. Let stand several hours before serving.